1. Field of the Invention
The invention relates to an apparatus for moulding moulded articles and specifically to an apparatus for moulding three-dimensionally deformed moulded articles from binder-containing web-like non-woven fabrics.
2. Description of the Prior Art
It is known that during the shaping of fibrous materials in the form of stretched materials, such as binder-containing cellulose chips, moulded articles can be produced by pressure and heat action, but that even with relatively small bending radii it is to be expected that a uniform displacement of the structure of the material beyond the average stretching length can no longer be ensured. To eliminate this problem a cold deformation takes place prior to the actual moulding process, the pre-mould being provided with a rubber covering which, as an elastic supporting surface, is intended to lead to a better distribution of the deformation stresses (Klauditz, W., E. Stegmann and W. Kratz: Untersuchungen uber die Herstellbarkeit und Eigenschaften einfacher Holzspan-Formteile, insbesondere fur den Mobelbau--Research on the possibilities of manufacture and the characteristics of wood shaving moulded articles, particularly for making furniture--Cologne and Opladen 1965, pp. 37/38).
This procedure is further developed by a known apparatus for producing pre-shaped articles from lignocellulose tangled fibre fleeces with stepwise shaping in moulds. The shaping surface thereof comprises a plurality of partial surfaces which can be moved relative to one another, the shaping partial surfaces of at least one mould half jointly acting on at least one elastically deformable, continuous intermediate layer in the form of a supporting layer. The shaping forces are transferred by the supporting layer to the fibrous fleece, the elastically deformable supporting layer, e.g. in the form of an endless belt, being fixed to a frame structure or held in movable manner with respect to the mould (DOS No. 27 01 480).
This known apparatus has advantageously made it possible to mould flat non-woven fabrics, i.e. those moulding blanks which can only be subject to limited tensile and crushing forces during the moulding process, to relatively highly curved moulded articles without the aforementioned disadvantages occurring. The locally increased expansion and crushing forces are largely absorbed and distributed by the elastically deformable supporting layer before the shaping forces can be transferred to the non-woven fabric. However, in the case of even greater local stretching the inherent elasticity of the supporting layer is often inadequate to cancel out its elongation so that the supporting layer becomes unusable after a relatively short time, which is disadvantageous from the cost standpoint. A change of the supporting layer material to give a greater elasticity only helps to a limited extent, because although it is necessary for these stabilizing supporting layers to easily adapt to any desired three-dimensional shape with in part considerable local elongation zones, whilst as far as possible any permanent deformation is rapidly cancelled out after each moulding process by the actual supporting layer material, the stabilizing action of the supporting layer, i.e. its surface distribution of local elongation and crushing, must as far as possible be adapted to the fibre covering length in the material to be deformed in order to prevent the formation of tears and unallowed thinning out, which is in turn only possible with a supporting layer made from a material whose inherent elasticity is not too low. Thus, although supporting layers with a relatively small elastic extensibility permit an advantageous local distribution of shear forces and the like over the stressed areas of the non-woven fabric to be deformed, their elasticity is not then adequately reversible to be able to successively use the same supporting layer for a plurality of moulding processes.
This disadvantage is also encountered with another known apparatus (DOS No. 27 13 527) in which inter alia fabrics made from stabilizing layers or deformable supporting layers are used and which is characterized in that they have no significant inherent elasticity.
The problem of the present invention is to so further develop and improve an apparatus for moulding three-dimensionally deformed moulded articles such that the deformation behaviour of the stabilizing supporting layer can be matched in an optimum manner to the deformation behaviour of the non-woven fabric without there being any risk of over-elongation of the supporting layer in order to enable the latter to be used repeatedly.